Trouble with updating Fairphone Updater


I am experiencing trouble with updating my Fairphone Updater app on Fairphone 2. I was intending to participate in the beta programme and get the pre-release version of Android 9, since it is now possible to install it as a normal update. The release does not show up in Fairphone Updater, so I thought I should probably update Fairphone Updater itself.
I have tried installing the apk of the newest version of Fairphone Updater as the instructions suggest, but unfortunately I get a notice that translates “The app was not installed. The package is evidently damaged.” (In German: “App wurde nicht installiert. Das Paket ist offenbar beschädigt.”)
Now I know I could install the update manually or try a factory reset, but both are no viable options for me. As I am not using a Google account and not using many standard Google apps, regaining my apps and app settings would take me many hours.
So is there any solution to get the Fairphone Updater update to work (and the Android update subsequently)?
Thanks in advance for your help!

Best regards

5 posts were merged into an existing topic: FP2: Fairphone OS 21.01.0-rel.0 (Android 9 release candidate)